Audi's rotary power shock

Audi's plug-in electric A1 e-Tron can be recharged using a regular powerpoint, but it also gets a rotary engine similar to a Mazda RX sports cars.

March 3 2010

Toby Hagon

Audi A1 e-Tron

Audi A1 e-Tron

Audi A1 e-Tron

of

Audi has revived the quirky rotary engine that has been used exclusively in Mazda RX models such as the RX-7 and RX-8 for more than two decades.

The tiny 0.25-litre (254cc) single piston 'Wankel' engine acts as a range extender in the Audi A1 e-Tron electric car, which can drive up to 50km on electricity alone.

Instead of pistons that move up and down the piston spins around an axis making for smooth running and reducing stress on some components.

Rotary engines were once considered the next big thing and capable of overtaking the four-stroke engines used in all modern cars. But increased development and efficiencies injected life into the regular piston engines.

The tiny engine in the Audi e-Tron has been designed to operate at a single speed - 5,000rpm - allowing engineers to tune it for the specific task of recharging the car's lithium ion batteries.

Like other so-called plug-in hybrid cars, the Audi e-Tron's petrol rotary engine never actually drives the wheels, instead just charging the battery in an effort to improve efficiency.

It musters only 15kW of power, about one-eighth an average small car.

Audi says the e-Tron uses a claimed average of 1.9 litres of fuel per 100km (using the government-derived formula), which is about one quarter an average small car.

It has a 12 litre fuel tank, which takes overall driving range for the Audi A1 e-Tron to 250km, about half of what you'd expect from many of similarly sized vehicles.

"This is the next baby within the e-Tron family," and Audi spokesman said. "We're thinking boldly along new lines."

It is expected that the Audi e-Tron will be able to be fully recharged in around five hours from a regular 240V outlet.